An enormous mushroom cloud formed in the sky over Beijing late last week, sparking fears that a cataclysmic, Armageddon-like event was underway.Alas, it was not the end of the world—or worse, the beginning of a real-life movie starring Will Smith: It was just nature.The giant cumulonimbus—which spanned several miles—was accompanied by lightning, swallowing up the capital's skyline for an hour, according to the Daily Mail.